When van der Waals Met Kagome: A 2D Antimonide with a Vanadium-Kagome Network

Abstract

2D materials showcase unconventional properties emerging from quantum confinement effects. In this work, a “soft chemical” route allows for the deintercalation of K⁺ from the layered antimonide KV₆Sb₆, resulting in the discovery of a new metastable 2D-Kagome antimonide K_0.1(1)V₆Sb₆ with a van der Waals gap of 3.2 Å. The structure of K_0.1(1)V₆Sb₆ was determined via the synergistic techniques, including X-ray pair distribution function analysis, advanced transmission electron microscopy, and density functional theory calculations. The K_0.1(1)V₆Sb₆ compound crystallizes in the monoclinic space group C2/m (a = 9.57(2) Å, b = 5.502(8) Å, c = 10.23(2) Å, β = 97.6(2)°, Z = 2). The [V₆Sb₆] layers in K_0.1(1)V₆Sb₆ are retained upon deintercalation and closely resemble the layers in the parent compound, yet deintercalation results in a relative shift of the adjacent [V₆Sb₆] layers. The magnetic properties of the K_0.1(1)V₆Sb₆ phase in the 2–300 K range are comparable to those of KV₆Sb₆ and another Kagome antimonide KV₃Sb₅, consistent with nearly temperature-independent paramagnetism. Electronic band structure calculation suggests a nontrivial band topology with flat bands and opening of band crossing afforded by deintercalation. Transport property measurements reveal a metallic nature for K_0.1(1)V₆Sb₆ and a low thermal conductivity of 0.6 W K^–1 m^–1 at 300 K. Additionally, ion exchange in KV₆Sb₆ via a solvothermal route leads to a successful partial exchange of K⁺ with A⁺ (A = Na, Rb, and Cs). This study highlights the tunability of the layered structure of the KV₆Sb₆ compound, providing a rich playground for the realization of new 2D materials.